Learning to play any musical instrument involves the development and subsequent integration of numerous new skills in a way that is foreign to the student. There are new sensorimotor skills associated with the mechanics of the instrument that must be learned. There are cognitive skills that must be learned as well, not the least of which involves learning a complex new symbolic and auditory language. All of these skills must be integrated and assimilated in real time, while simultaneously being driven by the student's emotional expression of the music. In the end, producing music can be described as an expression of the simultaneous combined output of one's sensorimotor coordination, cognition, and emotional self (i.e., technique+human expression=art). The mastery of these technical skills along with their fluid integration frees an artist to convey or express all that is held within the emotional self.
Within the musical field, the trombone is known to have a relatively long learning curve compared to other instruments such as piano or saxophone. This is due to inherent difficulties in playing the trombone posed by its design. First, the trombone is a brass instrument. At their core, brass instruments produce sound via vibrations of the lips powered by the expiratory respiration muscles. This is not true of any other instrument group. Tone quality, pitch, range, and accuracy all require coordination between large expiratory muscle groups and the relatively much smaller orbicularis oris, buccal, and other facial muscles (embouchure), along with control of the relative size of the oral cavity and throat. The characteristic of the very beginning of a note as well as the note's length is accomplished with coordinated effort of the tongue and the respiratory muscles. This is referred to musically as articulation and is somewhat analogous to speaking, but requires additional effort for the development and integration of skills necessary to play with accurate pitch (i.e., to “play in tune”).
A second aspect of the trombone that affects the difficulty of learning to play the instrument is its design. Although not appreciated by most, this instrument is especially hard to hold properly, especially by children and/or individuals with small or weak hands. Embouchure tension and hence, pitch, is affected by direct mouthpiece pressure, so holding the instrument in an unsteady or inconsistent way during playing will result in pitch fluctuations. Accordingly, when not held properly, the development of certain skills is impeded.
The design of the trombone also impacts playing difficulty since it is the only brass instrument that employs a slide-based system of operation. All common brass instruments except the trombone use valves to add mixed lengths of tubing to the air path in order to play the desired pitches. The accuracy of these additional lengths of tubing is inherently “guaranteed” simply by fully depressing the appropriate valve(s). The pitch controlling system employed by the trombone is much simpler, but much more difficult to learn and master since position locations are rather arbitrary. As was originally designed and is commonly embodied, the trombone has infinite control of tubing length throughout its range via the slide, which in essence is a relatively long, U-shaped section of telescopic tubing. The slide has no direct mechanism to provide accurate feedback as to how much length to add to produce a desired pitch.
In common practice, there are 7 recognized basic trombone slide “positions” which are described as approximate distances by visual reference, comparing a certain part of the moveable portion of the slide with the rim of the bell of the trombone and with parts of the end of the stationary part of the slide, commonly referred to as the “stockings”. A player must learn these positions through a long and tedious development process, at first using these rather arbitrary visual cues, and over time (commonly 5 years to over a decade) eventually learning to incorporate auditory sensory feedback (e.g., by carefully developing the ability to hear his/her own sound's pitch while comparing it to both memorized pitch intervals and other musical instruments such as the piano) and then making adjustments to slide position as necessary. As this process develops, constant repetition over years of dedicated work eventually results in a form of memorized hand, arm, and shoulder positions. Furthermore, since pitch when playing the trombone is directly affected by embouchure tension, exhalation force, and also the slide position, and each of these elements is a continuous variable, a player needs to constantly monitor and quickly make slight adjustments to one or more of these variables to play accurately in terms of pitch. Hence, in the beginning, the fact that the embouchure takes (at the very least) many years to develop a degree of repeatable accuracy, even after developing the skill and focus to listen to the student's own pitch and make comparisons to other references, pitch accuracy is a moving target that commonly requires many more years to achieve a degree of mastery. Even by a typical master during performance, accuracy and repeatability in terms of measurable displacements may be a skill that is in constant flux to the extent that humans are not machines.
Accordingly, the introduction of an aide that brings consistency to any of the elements of pedagogy described above would be expected to shorten the learning curve for learning to play the trombone.